U.S. patent application number 12/581051 was filed with the patent office on 2011-04-21 for eyeglasses with a planar array of microphones for assisting hearing.
This patent application is currently assigned to NXP B.V.. Invention is credited to RENE MARTINUS MARIA DERKX.
Application Number | 20110091057 12/581051 |
Document ID | / |
Family ID | 43437260 |
Filed Date | 2011-04-21 |
United States Patent
Application |
20110091057 |
Kind Code |
A1 |
DERKX; RENE MARTINUS MARIA |
April 21, 2011 |
EYEGLASSES WITH A PLANAR ARRAY OF MICROPHONES FOR ASSISTING
HEARING
Abstract
An apparatus implements directional sound detection. The
apparatus includes a portable hearing aid device, a plurality of
sound detectors, and electronic circuitry. The sound detectors are
coupled to the portable hearing aid device. The sound detectors are
arranged in a substantially planar array which is located in
approximately a two-dimensional plane which extends through both a
listener position and a sound generator position. The electronic
circuitry is electronically coupled to the plurality of sound
detectors. The electronic circuitry generates a reproduced sound
signal based on sound signals from at least a subset of the
plurality of sound detectors. The subset includes at least two
sound detectors in a one-dimensional line and at least one sound
detector located within the two-dimensional plane other than along
the one-dimensional line.
Inventors: |
DERKX; RENE MARTINUS MARIA;
(EINDHOVEN, NL) |
Assignee: |
NXP B.V.
Eindhoven
NL
|
Family ID: |
43437260 |
Appl. No.: |
12/581051 |
Filed: |
October 16, 2009 |
Current U.S.
Class: |
381/313 ;
381/327 |
Current CPC
Class: |
H04R 2430/20 20130101;
H04R 25/407 20130101; H04R 2201/401 20130101 |
Class at
Publication: |
381/313 ;
381/327 |
International
Class: |
H04R 25/00 20060101
H04R025/00 |
Claims
1. An apparatus for directional sound detection, the apparatus
comprising: a portable hearing aid device; a plurality of sound
detectors coupled to the portable hearing aid device, wherein the
sound detectors are arranged in a substantially planar array which
is located in approximately a two-dimensional plane which extends
through both a listener position and a sound generator position;
and electronic circuitry electronically coupled to the plurality of
sound detectors, wherein the electronic circuitry is configured to
generate a reproduced sound signal based on sound signals from at
least a subset of the plurality of sound detectors, wherein the
subset comprises at least two sound detectors in a one-dimensional
line and at least one sound detector located within the
two-dimensional plane other than along the one-dimensional
line.
2. The apparatus of claim 1, wherein the subset of the sound
detectors comprises at least three sound detectors, and the
electronic circuitry is configured to combine the sound signals to
generate the reproduced sound signal based on a first-order
steerable superdirectional response using the sound signals from
the at least three sound detectors.
3. The apparatus of claim 1, wherein the subset of the sound
detectors comprises at least four sound detectors, and the
electronic circuitry is configured to combine the sound signals to
generate the reproduced sound signal based on a second-order
steerable superdirectional response using the sound signals from
the at least four sound detectors.
4. The apparatus of claim 1, wherein the electronic circuitry is
configured to combine the sound signals from the subset of the
sound detectors to generate substantially a unity response at a
listening angle toward the sound generator position.
5. The apparatus of claim 1, wherein the electronic circuitry is
configured to combine the sound signals from the subset of the
sound detectors to generate substantially a null response at an
interference angle toward an interference sound position.
6. The apparatus of claim 1, further comprising an audio speaker
coupled to the electronic circuitry, wherein the audio speaker is
configured to generate an audible sound representative of the
reproduced sound signal.
7. The apparatus of claim 1, wherein the electronic circuitry
comprises a digital signal processor (DSP).
8. The apparatus of claim 7, wherein the electronic circuitry
further comprises: an analog-to-digital converter (ADC) coupled to
the digital signal processor, wherein the analog-to-digital
converter is configured to generate digital representations of the
sound signals from the sound detectors; and a digital-to-analog
converter (DAC) coupled to the digital signal processor, wherein
the digital-to-analog converter is configured to generate an analog
representation of the reproduced sound signal.
9. The apparatus of claim 7, wherein the electronic circuitry
comprises a controller to control a directivity angle of a
superdirectional response based on the sound signals from the sound
detectors.
10. A pair of hearing glasses comprising: a pair of optical
elements; a frame comprising a front portion and two stems, wherein
the front portion is configured to hold the pair of optical
elements, and the stems are configured to hold the frame in a
position relative to a user's head; and a hearing aid device
coupled to the frame, wherein the hearing aid device comprises: a
planar array of at least three sound detectors, wherein at least
one sound detector is coupled to the front portion of the frame,
and at least one sound detector is coupled to one of the stems; and
electronic circuitry electronically coupled to the planar array of
sound detectors and configured to generate a reproduced sound
signal based on sound signals from the planar array of sound
detectors.
11. The pair of hearing glasses of claim 10, wherein the electronic
circuitry is configured to combine the sound signals to generate
the reproduced sound signal based on a first-order steerable
superdirectional response using the at least three sound
detectors.
12. The pair of hearing glasses of claim 10, wherein the planar
array comprises at least four sound detectors, wherein the
electronic circuitry is configured to combine the sound signals to
generate the reproduced sound signal based on a second-order
steerable superdirectional response using the at least four sound
detectors.
13. The pair of hearing glasses of claim 10, wherein the electronic
circuitry further comprises: a digital signal processor (DSP) to
digitally process the sound signals from the planar array of sound
detectors to generate the reproduced sound signal; and an audio
speaker coupled to the digital signal processor, wherein the audio
speaker is configured to generate an audible sound representative
of the reproduced sound signal.
14. The pair of hearing glasses of claim 13, wherein the audio
speaker comprises a personal audio speaker to generate the audible
sound with sound wave characteristics that allow the audible sound
to be heard primarily within the vicinity of a user's ear.
15. The pair of hearing glasses of claim 10, wherein the electronic
circuitry further comprises a controller to control a directivity
angle of a superdirectional response based on the sound signals
from the sound detectors.
16. The pair of hearing glasses of claim 10, wherein the electronic
circuitry further comprises a controller allow a user to select
between one of a plurality of operating modes, wherein the
operating modes comprise: a planar array operating mode in which
the electronic circuitry is configured to generate the reproduced
sound signal based on sound signals from the planar array of sound
detectors; and a line array operating mode in which the electronic
circuitry is configured to generate another reproduced sound signal
based on sound signals from a line array of a plurality of sound
detectors arranged in a line array configuration within the planar
array.
17. The pair of hearing glasses of claim 10, wherein the electronic
circuitry is configured to combine the sound signals from the
planar array of sound detectors to generate substantially a unity
response at a listening angle toward a position of a sound
generator and to place substantially a null response at an
interference angle toward a position of an interference sound
source.
18. A method for controlling directivity of a hearing aid device,
the method comprising: detecting sound waves at a plurality of
sound detectors coupled to a portable hearing aid device, wherein
the sound detectors are arranged in a substantially planar array
which is located in approximately a two-dimensional plane which
extends through both a listener position and a sound generator
position; generating a reproduced sound signal based on sound
signals from at least a subset of the plurality of sound detectors,
wherein the subset comprises at least two sound detectors in a
one-dimensional line and at least one sound detector located within
the two-dimensional plane other than along the one-dimensional
line; and generating an audible sound representative of the
reproduced sound signal and communicating the audible sound to a
user of the portable hearing aid device.
19. The method of claim 18, further comprising: digitally combining
the sound signals from at least four sound detectors; and
generating the reproduced sound signal based on a second-order
steerable superdirectional response using the combined sound
signals from the at least four sound detectors.
20. The method of claim 19, wherein digitally combining the sound
signals from the sound detectors further comprises: generating
substantially a unity response at a listening angle toward the
sound generator position; and generating substantially a null
response at an interference angle toward an interference sound
position, wherein the interference angle is at approximately 45
degrees from the listening angle for a first-order response and
approximately 30 degrees from the listening angle for a
second-order response.
Description
[0001] There are many people around the world who deal with hearing
loss. In some cases, hearing aid devices can be used to help people
improve their hearing despite natural losses in high-frequency
discrimination. Hearing aid devices typically amplify sounds so
that the user can hear the sounds more easily. Unfortunately, many
conventional hearing aid devices amplify all sounds, including
ambient noise, making it difficult to distinguish an intended
source (e.g., a person's voice) from the rest of the ambient
noise.
[0002] One conventional solution to the problem of amplified
ambient noise is the use of in-ear digital hearing aids. Such
hearing aids include multiple microphones that provide tunable
directionality so that a hearing aid has a preferred direction of
sensitivity, usually tuned to be forward facing. In this way, the
hearing aid increases the sound from the conversation ahead of the
user, without increasing all of the background noise.
[0003] Another conventional solution for this problem of amplified
ambient noise is implemented in eyeglasses which can be worn by the
user. The eyeglasses incorporate hearing aid devices and, hence,
are sometimes referred to as "hearing-glasses." One company that
manufactures such hearing-glasses is Varibel (www.varibel.nl) of
Brussels, Belgium. The hearing-glasses manufactured by Varibel use
an end-fire array of microphones which are mounted on the stems of
the glasses. The end-fire array of microphones has an increased
sensitivity to sounds waves which originate from a source that is
approximately in line with the axis of the array (i.e., in front of
the user).
[0004] With the hearing-glasses from Varibel, the sound from the
front is amplified and the diffuse noise coming from other
directions is reduced relative to the intended sound. The technical
term that is used to measure the diffuse noise reduction is called
the directivity index (DI), which equals:
DI = 10 log 10 ( Q ) , where ##EQU00001## Q = 4 .pi. E 2 ( .pi. / 2
, 0 ) .intg. .phi. = 0 2 .pi. .intg. .theta. = 0 .pi. E 2 ( .theta.
, .phi. ) sin .theta. .theta. .phi. ##EQU00001.2##
in which .phi.,.theta. are the standard spherical coordinate system
parameters (azimuth and elevation, respectively), E is the
directional response, and the look direction is given by
.theta.=.pi./2 and .phi.=0. In a specific example using four
microphones in an end-fire array configuration, the hearing-glasses
of Varibel use first- and second-order superdirectional processing
to obtain a weighted directivity index of 8.2 dB.
[0005] Other conventional hearing-glasses use a broad-side array of
microphones which are mounted to the front portion of the glasses.
The broad-side array of microphones has an increased sensitivity to
sound waves that originate from a source that is approximately
perpendicular to the axis of the array. However, for wavelengths
larger than the spacing of the microphone array, the directivity
index is poor for broad-side arrays. Therefore, the end-fire array
is typically preferred for such wavelengths. The specific
characteristics of the detection beam patterns of various end-fire
and broad-side arrays depends on several factors, including the
sensitivity of the individual microphones and the spacing between
the microphones. Hereafter, only distances which are smaller than
the wavelengths of interest are considered for the spacing between
the microphones.
[0006] Whether an end-fire or a broad-side array is used on the
hearing-glasses, the directivity of the array of microphones is
typically substantially forward of the person wearing the glasses.
While these conventional array configurations help increase the
hearing sensitivity of the user in the general direction that the
user may be looking, end-fire and broad-side array configurations
are not optimal to suppress noise from an interference noise source
that is positioned close to the angle of the intended sound
generator. Specifically, with an end-fire array, only the
directivity index (reduction for diffuse noise coming from all
directions) is improved. The directivity index can also be improved
for a broad-side array. However, this improvement is lower compared
with the improvement for an end-fire array. Furthermore, at least
three microphones in a line-array and second- or higher-order
beamformers are required to obtain this improvement. However,
second- and higher-order beamformers are difficult to realize in
practice. Also, it is difficult for such broad-side arrays to
suppress noise from an interference source that is positioned close
to the angle of the intended sound generator. As one example, the
hearing aid user may have difficulty distinguishing between the
sound from a person with whom the user is talking (and facing) and
the noise from another person that is talking near the person with
whom the user is talking. In other words, it is difficult to
suppress noises that originate within the detection beam pattern of
the conventional end-fire and broad-side arrays.
[0007] Embodiments of an apparatus are described. In one
embodiment, the apparatus implements directional sound detection.
An embodiment of the apparatus includes a portable hearing aid
device, a plurality of sound detectors, and electronic circuitry.
The sound detectors are coupled to the portable hearing aid device.
The sound detectors are arranged in a substantially planar array
which is located in approximately a two-dimensional plane which
extends through both a listener position and a sound generator
position. The electronic circuitry is electronically coupled to the
plurality of sound detectors. The electronic circuitry generates a
reproduced sound signal based on sound signals from at least a
subset of the plurality of sound detectors. The subset includes at
least two sound detectors in a one-dimensional line and at least
one sound detector located within the two-dimensional plane other
than along the one-dimensional line. Other embodiments of the
apparatus are also described.
[0008] Embodiments of a pair of hearing glasses are also described.
In one embodiment, the hearing glasses include a pair of optical
elements, a frame, and a hearing aid device. The optical elements
are conventional lenses used in a pair of eyeglasses. The frame
includes a front portion and two stems. The front portion holds the
pair of optical elements. The stems hold the frame in a position
relative to a user's head. The hearing aid device is coupled to the
frame. In one embodiment, the hearing aid device includes a planar
array of sound detectors and electronic circuitry. The planar array
includes at least three sound detectors, of which at least one
sound detector is coupled to the front portion of the frame, and at
least one sound detector is coupled to one of the stems. The
electronic circuitry is electronically coupled to the planar array
of sound detectors to generate a reproduced sound signal based on
sound signals from the planar array of sound detectors. Other
embodiments of the hearing glasses are also described.
[0009] Embodiments of a method are also described. In one
embodiment, the method is a method for controlling directivity of a
hearing aid device. An embodiment of the method includes detecting
sound waves at a plurality of sound detectors coupled to a portable
hearing aid device. The sound detectors are arranged in a
substantially planar array which is located in approximately a
two-dimensional plane which extends through both a listener
position and a sound generator position. The method also includes
generating a reproduced sound signal based on sound signals from at
least a subset of the plurality of sound detectors. The subset
includes at least two sound detectors in a one-dimensional line and
at least one sound detector located within the two-dimensional
plane other than along the one-dimensional line. The method also
includes generating an audible sound representative of the
reproduced sound signal and communicating the audible sound to a
user of the portable hearing aid device. Other embodiments of the
method are also described.
[0010] Other aspects and advantages of embodiments of the present
invention will become apparent from the following detailed
description, taken in conjunction with the accompanying drawings,
illustrated by way of example of the principles of the
invention.
[0011] FIG. 1 depicts a schematic diagram of one embodiment of a
listening arrangement.
[0012] FIG. 2 depicts a schematic diagram of one embodiment of a
planar array of sound detectors for use in the listening
arrangement of FIG. 1.
[0013] FIG. 3 depicts a schematic diagram of another embodiment of
a planar array of sound detectors for use in the listening
arrangement of FIG. 1.
[0014] FIG. 4 depicts a schematic block diagram of one embodiment
of an apparatus for directional sound detection.
[0015] FIG. 5 depicts a diagram of one embodiment of a pair of
hearing glasses with a planar array of sound detectors coupled to
the frame of the hearing glasses.
[0016] FIG. 6 depicts a flow chart diagram of one embodiment of a
method for controlling directivity of a hearing aid device.
[0017] Throughout the description, similar reference numbers may be
used to identify similar elements.
[0018] It will be readily understood that the components of the
embodiments as generally described herein and illustrated in the
appended figures could be arranged and designed in a wide variety
of different configurations. Thus, the following more detailed
description of various embodiments, as represented in the figures,
is not intended to limit the scope of the present disclosure, but
is merely representative of various embodiments. While the various
aspects of the embodiments are presented in drawings, the drawings
are not necessarily drawn to scale unless specifically
indicated.
[0019] The present invention may be embodied in other specific
forms without departing from its spirit or essential
characteristics. The described embodiments are to be considered in
all respects only as illustrative and not restrictive. The scope of
the invention is, therefore, indicated by the appended claims
rather than by this detailed description. All changes which come
within the meaning and range of equivalency of the claims are to be
embraced within their scope.
[0020] Reference throughout this specification to features,
advantages, or similar language does not imply that all of the
features and advantages that may be realized with the present
invention should be or are in any single embodiment of the
invention. Rather, language referring to the features and
advantages is understood to mean that a specific feature,
advantage, or characteristic described in connection with an
embodiment is included in at least one embodiment of the present
invention. Thus, discussions of the features and advantages, and
similar language, throughout this specification may, but do not
necessarily, refer to the same embodiment.
[0021] Furthermore, the described features, advantages, and
characteristics of the invention may be combined in any suitable
manner in one or more embodiments. One skilled in the relevant art
will recognize, in light of the description herein, that the
invention can be practiced without one or more of the specific
features or advantages of a particular embodiment. In other
instances, additional features and advantages may be recognized in
certain embodiments that may not be present in all embodiments of
the invention.
[0022] Reference throughout this specification to "one embodiment,"
"an embodiment," or similar language means that a particular
feature, structure, or characteristic described in connection with
the indicated embodiment is included in at least one embodiment of
the present invention. Thus, the phrases "in one embodiment," "in
an embodiment," and similar language throughout this specification
may, but do not necessarily, all refer to the same embodiment.
[0023] While many embodiments are described herein, at least some
of the described embodiments function to construct a steerable
beam-pattern where a null is placed toward the angle of the
point-interferer while maintaining a unity response to the
listening angle and still having sufficient diffuse noise
reduction. The type of a null-steering scheme allows the rejection
of noise from an interferer near the listening angle. Also, at
least some embodiments implement hearing-glasses with a planar
array of microphones which provides a superdirectional beam-pattern
synthesis with the rejection of noise from an interferer, even if
the interferer is close to the listening angle.
[0024] FIG. 1 depicts a schematic diagram of one embodiment of a
listening arrangement 100. The illustrated listening arrangement
100 depicts the positions of various participants in a conversation
or other listening environment. In particular, the illustrated
listening arrangement 100 includes a listener 102 (designated as
"L"), a sound generator 104 (designated as "G"), and an
interference sound source 106 (designated as "I"). For convenience,
the listener 102, sound generator 104, and interference sound
source 106 are each described herein as humans who generate or
listen to audible sounds (e.g., during a conversation). However, in
some embodiments, the listener 102, sound generator 104, and/or
interference noise source 106 may be another type of animal or
machine capable of generating audible sounds.
[0025] As a matter of convention for the description herein, the
listener 102 is regarded as a person who is trying to listen to the
sounds (e.g., speech) generated by the sound generator 104. The
sounds generated by the sound generator 104 travel through space as
sound waves 108, depicted by the arrow between the sound generator
104 and the listener 102. Also, the interference sound source 106
may generate separate sounds which are designated as interference
noise because the listener 102 deems such sounds as interfering
with the sounds from the sound generator 104. The sounds generated
by the interference sound source 106 propagate through space as
sound waves 110, depicted by the arrow between the interference
sound source 106 and the listener 102. The angle, .beta., between
the sound generator 104 and the interference sound source 106,
relative to the listener 102, is referred to herein as the angular
difference between the sound generator 104 and the interference
sound source 106.
[0026] FIG. 2 depicts a schematic diagram of one embodiment of a
planar array 112 of sound detectors for use in the listening
arrangement 100 of FIG. 1. In one embodiment, the planar array 112
of sound detectors is incorporated with a hearing aid device so
that the listener 102 can more easily hear and understand the sound
generated by the sound generator 104. In one embodiment, the
hearing aid device is a portable hearing aid device.
[0027] For reference, the sound detectors are arranged in a
substantially planar array 112 which is located in approximately a
two-dimensional (2D) plane (depicted by the dashed lines forming a
parallelogram in FIG. 2). In the depicted embodiment, the
two-dimensional plane extends through the positions of the listener
102 and the sound generator 104. The two-dimensional plane also
extends through the position of the interference sound source 106.
Although the planar array 112 is referred to herein as being within
the two-dimensional plane, other embodiments may include additional
sound detectors that are outside of the two-dimensional plane.
Hence, the array of sound detectors is not necessarily limited to a
two-dimensional plane, so long as the sound detectors are arranged
in some form of multi-dimensional configuration, rather than
substantially in a line such as an end-fire or broad-side
array.
[0028] Electronic circuitry (refer to FIG. 4) manipulates the sound
signals generated by some or all of the sound detectors in the
planar array 112 in order to generate a reproduced sound signal
which allows the listener 102 to more easily hear and understand
the sounds from the sound generator 104. In circumstances where
sound signals from less than all of the sound detectors are used to
generate the reproduced sound signal, the operative sound detectors
nevertheless should be arranged in a substantially planar,
two-dimensional pattern. Thus, at least two sound detectors may be
a one-dimensional line, and at least one other sound detector is
located within the two-dimensional plane other than along the
one-dimensional line.
[0029] In general, the electronic circuitry combines the sound
signals to generate substantially a unity response 114 at a
listening angle toward the position of the sound generator 104. In
general, a unity response at a certain listening angle means that
the response at this angle is equal to the response of a single
omnidirectional microphone at this angle. The electronic circuitry
also generates substantially a null response at an interference
angle toward the position of the interference sound source 106. A
null response at a certain listening angle means that the response
is substantially lower (in theory, infinitely lower) than the
response of a single omnidirectional microphone at this angle.
[0030] In some embodiments, a subset of the sound detectors, rather
than all of the sound detectors in the planar array 112, may be
used in order to alleviate sensor noise problems in the
construction of superdirectional responses. As one example, the
electronic circuitry uses the sound signals from a subset of at
least three sound detectors (e.g., the sound detectors 116a, 116b,
and 116c shown in FIG. 5). More specifically, the electronic
circuitry combines the sound signals to generate the reproduced
sound signal based on a first-order steerable superdirectional
response.
[0031] By using a circular array of at least three omnidirectional
sound detectors, or sensors, in a planar geometry and the
application of signal processing techniques, it is possible to
construct a first-order superdirectional response that can be
steered with its main-lobe to any desired azimuthal angle and can
be adjusted to have any first-order directivity pattern (cardioid,
hypercardioid, etc.). This construction is performed via so-called
zeroeth- and first-order eigenbeams. For wavelengths larger than
the size of the array, and assuming that there is no sensor-noise,
the responses of the eigenbeams are frequency invariant and ideally
equal to:
E.sub.m=1
E.sub.d.sup.0(.theta.,.phi.)=cos(.phi.)sin(.theta.)
E.sub.d.sup..pi./2(.theta.,.phi.)=cos(.phi.-.pi./2)sin(.theta.)
in which .phi.,.theta. are the standard spherical coordinate
angles: elevation and azimuth.
[0032] The zeroeth-order eigenbeam E.sub.m represents the monopole
response, while the first-order eigenbeams
E.sub.d.sup.0(.theta.,.phi.) and E.sub.d.sup..pi./2(.theta.,.phi.)
represent the orthogonal dipole responses.
[0033] The dipole response can be steered to any angle,
.phi..sub.s, by means of a weighted combination of the orthogonal
dipole pair:
E.sub.d.sup..phi..sup.s(.theta.,.phi.)=cos(.phi..sub.s)E.sub.d.sup.0(.th-
eta.,.phi.)+sin(.phi..sub.s)E.sub.d.sup..pi./2(.theta.,.phi.)
with 0.ltoreq..phi..sub.s.ltoreq.2.pi. as the steering angle.
[0034] The steered and scaled superdirectional microphone response
can be constructed via:
E ( .theta. , .phi. ) = S [ .alpha. E m + ( 1 - .alpha. ) E d .PHI.
s ( .theta. , .phi. ) ] = S [ .alpha. + ( 1 - .alpha. ) cos ( .phi.
- .PHI. s ) sin ( .theta. ) ] ##EQU00002##
with .alpha..ltoreq.1 as the parameter for controlling the
directional pattern of the first-order response, and S as an
arbitrary scaling factor (which can also have a negative
value).
[0035] It should be noted that the foregoing equations may be based
on an assumption that there is a unity response of the
superdirectional microphone for a desired source coming from an
arbitrary azimuthal angle, .phi., and for an elevation angle of
.theta.=.pi./2.
[0036] In some embodiments, the directivity factor, Q, is optimized
under the constraints that a unity response is obtained at the
listening angle, {tilde over (.phi.)}.sub.s, and a null is obtained
at the interference angle, .phi..sub.n. The optimal pattern
synthesis for a first-order superdirectional response can be
constructed using:
S = 1 .alpha. + ( 1 - .alpha. ) cos ( .PHI. ~ s - .PHI. s ) , where
##EQU00003## .alpha. = cos ( .PHI. n - .PHI. s ) cos ( .PHI. n -
.PHI. s ) - 1 , and ##EQU00003.2## .PHI. s = .PHI. n - 2 arctan [ 1
- cos ( .PHI. n - .PHI. ~ s ) .+-. A 4 sin ( .PHI. n - .PHI. ~ s )
] , with ##EQU00003.3## A = cos 2 ( .PHI. ~ s - .PHI. n ) + 16 sin
2 ( .PHI. ~ s - .PHI. n ) - 2 cos ( .PHI. ~ s - .PHI. n ) + 1 - 64
cos ( .PHI. ~ s ) cos ( .PHI. n ) sin ( .PHI. ~ s ) sin ( .PHI. n )
##EQU00003.4##
[0037] As another example, the electronic circuitry uses the sound
signals from a subset of at least four sound detectors. In this
example, the electronic circuitry combines the sound signals to
generate the reproduced sound signal based on a second-order
steerable superdirectional response. However, it should be noted
that second-order beam patterns may be difficult to construct in
practice, especially for low-frequencies, where the wavelength is
much longer than the array size. Such difficulties are due, at
least in part, to the physical arrangement of the array, which may
be limited in overall size by the size of the frame to which the
individual sound detectors are mounted. Other embodiments may use
other combinations of sound detectors and generate other
directional responses.
[0038] FIG. 3 depicts a schematic diagram of another embodiment of
a planar array 112 of sound detectors 116 for use in the listening
arrangement 100 of FIG. 1. Compared with the illustrations of FIG.
1, the illustration of FIG. 3 depicts a top view of the listening
arrangement 100 of FIG. 1.
[0039] In the depicted embodiment, the sound detectors 116 are
coupled to a frame 118 which may be worn by the listener 102. One
example of a frame 118 that may be worn by a user is shown in FIG.
5 and described in more detail below. Other embodiments may use
other types of frames 118.
[0040] For convenience in describing one example of the operation
of the planar array 112, four of the sound detectors 116 shown in
the figure are black, while the remaining sound detectors are
white. In one embodiment, the indicated (i.e., black) sound
detectors 116 represent the subset of sound detectors 116 whose
sound signals are used by the electronic circuitry to generate the
reproduced sound signal. In one embodiment, the electronic
circuitry is included in a hearing aid 120 coupled to the frame
118. The hearing aid 120 may be physically and/or electronically
coupled to the frame 118. By processing the sound signals from the
indicated subset of sound detectors 116, the electronic circuitry
within the hearing aid 120 is able to form a beam pattern that
provides the unity response 114 directed toward the sound generator
104, while directing a null toward the interference sound source
106. Other embodiments may use other combinations and/or numbers of
sound detectors 116.
[0041] FIG. 4 depicts a schematic block diagram of one embodiment
of an apparatus 130 for directional sound detection. The
illustrated apparatus 130 includes a plurality of sound detectors
(M) 116 (arranged in a planar array), an analog-to-digital
converter (ADC) 132, a digital signal processor (DSP) 134, a
digital-to-analog converter (DAC) 136, and an audio speaker 138.
The illustrated apparatus 130 also includes a controller 140 and a
power supply 142. Although the apparatus 130 is shown and described
with certain components and functionality, other embodiments of the
apparatus 130 may include fewer or more components to implement
less or more functionality. For example, some embodiments of the
apparatus 130 may have filters (not shown), a user interface (not
shown), and so forth. For example, some embodiments include a
user-control button or selector (e.g., integrated with the
controller) for switching between end-fire and planar array
operating modes. In this manner, a user could select the end-fire
array operating mode for improved or optimal reduction of diffuse
noise. Alternatively, the user could select the planar array
operating mode for increased or optimal performance in the presence
of diffuse noise and interference noise close to the intended sound
generator 104.
[0042] In one embodiment, the analog-to-digital converter 132
converts one or more of the analog sound signals generated by the
sound detectors 116 into corresponding digital signals. The digital
signals also may be referred to as digital representations of the
analog signals. Although a single analog-to-digital converter 132
is shown, other embodiments may include more than one
analog-to-digital converter for faster processing of the sounds
signals from the individual sound detectors 116.
[0043] The digital signal processor 134 receives the digital
signals from the analog-to-digital converter 132 and generates the
reproduced sound signal to be communicated to the listener 102. In
one embodiment, the digital signal processor 134 processes the
sound signals according to an algorithm or instructions from the
controller 140. In this manner, the controller 140 may control a
directivity angle of a superdirectional response based on the sound
signals from the sound detectors 116. Further, in some embodiments,
the controller 140 may include additional processing and/or memory
resources. In other embodiments, the functionality of the
controller 140 may be incorporated into the digital signal
processor 134 or another component of the apparatus 130.
[0044] The digital signal processor 134 sends the digitally
reproduced sound signal to the digital-to-analog converter 136,
which converts the reproduced sound signal to an analog signal. The
analog signal also may be referred to as an analog representation
of the digitally reproduced sound signal. The digital-to-analog
converter 136 then sends the analog signal to the audio speaker 138
which generates an audible sound representative of the reproduced
sound signal. By listening to the audible sound from the speaker
138, the listener 102 is able to hear the sound generated by the
sound generator 104, without significant interference from the
interference sound source 106.
[0045] In one embodiment, the power supply 142 supplies power to
the various components of the apparatus 130. In a specific example,
the power supply 142 includes at least one battery and supplies a
direct current (DC) power signal at a suitable voltage to the
various components.
[0046] FIG. 5 depicts a diagram of one embodiment of a pair of
hearing glasses 150 with a planar array of sound detectors 116
coupled to the frame of the hearing glasses 150. In general, the
hearing glasses 150 may provide optical correction, similar to
conventional eyeglasses, by way of two optical elements 152. The
optical elements are conventionally mounted in a front portion 154
of the frame. Stems 156 on either side of the front portion 154
allow the user to wear the hearing glasses 150 and hold the frame
in position relative to the user's head (not shown).
[0047] In the illustrated embodiment, several sound detectors 116
are schematically shown at various mounting locations on the front
portion 154 and the stems 156 of the frame. More specifically, at
least one sound detector 116 is coupled to the front portion 156 of
the frame. Similarly, at least one sound detector 116 is coupled to
one of the stems 156. Although the sound detectors 116 are shown in
specific locations on the frame of the hearing glasses 150, other
embodiments may include fewer or more sound detectors 116 mounted
in similar or different locations on the frame.
[0048] Each of the sound detectors 116 is electronically coupled to
the electronic circuitry 158 mounted to the left stem 156 of the
hearing glasses 150. Electronic coupling may include physical
connections via wires, wireless connections via radio frequency
(RF) communications, of another similar type of coupling. In
another embodiment, the electronic circuitry 158 may be mounted in
a different location on the frame, or separated in multiple
locations on the frame, or partially or wholly located at a remote
location from the frame. As explained above, the electronic
circuitry 158 generates the reproduced sound signal based on the
sound signals from a planar array of sound detectors 116, including
some (i.e., a subset) or all of the sound detectors 116. Together,
the sound detectors 116, the electronic circuitry 158, and the
audio speaker 138 make up one embodiment of a hearing aid device.
In one embodiment, the audio speaker 138 is a personal audio
speaker to generate the audible sound with sound wave
characteristics that allow the audible sound to be heard primarily
within the vicinity of a user's ear. Other embodiments may use
other types of audio speakers or more than one audio speaker.
[0049] FIG. 6 depicts a flow chart diagram of one embodiment of a
method 160 for controlling directivity of a hearing aid device.
Although the method 160 is described in conjunction with the
devices illustrated in the previous figures, embodiments of the
method 160 may be implemented with other types of hearing aid
devices.
[0050] At block 162, the hearing aid device detects sound waves at
a plurality of sound detectors 116 coupled to a portable hearing
aid device. As explained above, the sound detectors 116 are
arranged in a planar array configuration. At block 164, the
electronic circuitry 158 combines the sound signals from at least a
subset of the sound detectors 116 to generate the reproduced sound
signal. Depending on the amount of directivity that is desired or
specified, the electronic circuitry 158 may combine the sound
signals according to an algorithm or other instructions. At block
166, the electronic circuitry 158 generates an audible sound
representative of the reproduced sound signal and, at block 168,
communicates the audible sound to a user of the portable hearing
aid device. In some embodiments, the operations of generating and
communicating the audible signal may be combined, for example,
where the audible signal is generated at a location that the user
can hear the generated audible signal. The depicted method 160 then
ends.
[0051] In further embodiments, the method 160 also may include
additional operations which may be further beneficial to the
operation of the portable hearing aid device. For example, in one
embodiment, the method 160 also includes digitally combining the
sound signals from at least three sound detectors and generating
the reproduced sound signal based on a first-order steerable
superdirectional response. In another embodiment, the method 160
also includes digitally combining the sound signals from at least
four sound detectors and generating the reproduced sound signal
based on a second-order steerable superdirectional response. In a
further embodiment, digitally combining the sound signals from the
sound detectors includes generating substantially a unity response
at a listening angle toward the sound generator position,
generating substantially a null response at an interference angle
toward an interference sound position, and improving the
directivity index (Q>1). For a first-order steerable
superdirectional response, the planar array 112 can have an
improvement of the directivity index even when suppressing an
interference noise at an angle of approximately 45 degrees from the
listening angle (e.g., .beta..gtoreq.45.degree.. In contrast, using
a conventional line array arrangement to suppress an interference
noise at this angle would result in a degradation of the
directivity index (Q<1). Thus, the conventional line array is
unable to maintain the directivity index while achieving good
suppression of the interference noise. For a second-order steerable
superdirectional response, the planar array 112 may exhibit an
improvement even when suppressing an interference noise at an angle
of approximately 30 degrees from the listening angle (e.g.,
.beta..gtoreq.30.degree.. In contrast, using a conventional line
array arrangement to suppress an interference noise at this angle
would result in a degradation of the directivity index (Q<1).
Again, the conventional line array is unable to maintain the
directivity index while achieving good suppression of the
interference noise. In these examples, the improvement of the
response may be approximately 2 dB. In other embodiments, the
improvement of the response may be more or less. Additionally, the
interference angle may be significantly smaller for both the first-
and second-order steerable superdirectional responses. For example,
the interference angle may be approximately 20, 15, 10, or even 5
degrees, although the diffuse response improvement may be
significantly less as the interference angle decreases.
[0052] In the above description, specific details of various
embodiments are provided. However, some embodiments may be
practiced with less than all of these specific details. In other
instances, certain methods, procedures, components, structures,
and/or functions are described in no more detail than to enable the
various embodiments of the invention, for the sake of brevity and
clarity.
[0053] Although the operations of the method(s) herein are shown
and described in a particular order, the order of the operations of
each method may be altered so that certain operations may be
performed in an inverse order or so that certain operations may be
performed, at least in part, concurrently with other operations. In
another embodiment, instructions or sub-operations of distinct
operations may be implemented in an intermittent and/or alternating
manner.
[0054] Although specific embodiments of the invention have been
described and illustrated, the invention is not to be limited to
the specific forms or arrangements of parts so described and
illustrated. The scope of the invention is to be defined by the
claims appended hereto and their equivalents.
* * * * *